Defining Diesel: Clearing Up Convoluted Fuel Terminology

What do the Inuit people and the fuel industry have in common? An inexplicably long list of words to describe one thing. While the Inuit may be in the lead with 50 different words for snow, fuel professionals aren’t that far behind with up to 25 terms to describe the fuel most commonly known as diesel.

Unless you are a refining engineer, it can be all too easy to get the words confused. This handy Q&A can help you keep things straight when it comes to the differences between the various kinds of diesel in the fuel supply.

What’s the difference between diesel, biodiesel, biodiesel blends and renewable diesel?

Diesel is a petroleum-based fuel that comes in two grades – Diesel No. 1 (1-D) and Diesel No. 2 (2-D). Diesel No. 2 is the most common grade of diesel used in the motor fuel supply. Other names for diesel include petroleum diesel, standard diesel, conventional diesel, fossil diesel and petrodiesel.

Biodiesel is created from biomass oils through a process called transesterification. Its ingredients include plant oils, cooking oil, animal fat and even algae. Also known as B100, biodiesel is most often used as a blendstock – not a transportation fuel.

Biodiesel blends represent the majority of the diesel fuel sold as transportation fuel. It is made by blending biodiesel into petroleum diesel or renewable diesel. Whereas most consumers refer to ethanol blends such as E10 as “gasoline,” biodiesel blends are similarly known to most people as just “diesel.” The classifications, such as B20 and B5, for biodiesel blends are determined by the percentage of biodiesel content contained in the fuel:

B20: The most common biodiesel blend, which ranges from 6% to 20% biodiesel.
B5: Contains 5% biodiesel and is most commonly used in fleet vehicles.

Renewable diesel, also sometimes called green diesel, is a biofuel but it is not biodiesel. While renewable diesel is made from the same renewable resources as biodiesel, it is created through a different process. In fact, renewable diesel is chemically identical to petroleum diesel and meets ASTM D975, the specification for petroleum diesel. As a result, renewable diesel can also be blended with biodiesel to make biodiesel blends such as B20 and B5.

What is highway diesel, non-road diesel and ultra low sulfur diesel?

Highway diesel, also called on-road and clear diesel, and off-road diesel, also called non-road diesel, non-highway diesel, ag diesel and red diesel, are the same from a chemical standpoint. However, these two classifications have different legal implications.

Off-road diesel is approved for use in vehicles/machinery that is not driven on the road, including farm equipment and heavy-duty earthmoving equipment. Because off-road diesel isn’t used for road transportation, there is no fuel tax included at sale. Off-road diesel is dyed red so that authorities can easily distinguish it from highway diesel. Those who are caught driving a road vehicle containing off-road diesel on public roads may be charged with tax evasion.

Ultra low sulfur diesel (ULSD) is a regulatory designation mandating a specific level of sulfur contained in diesel. Since 2010, the U.S. Environmental Protection Agency has required that all diesel fuel supplied for road transportation — and all highway diesel vehicles use — ULSD. ULSD contains just 15 parts per million of sulfur (prior to regulating sulfur content, diesel contained as much as 5,000 ppm of sulfur). This requirement was developed to reduce pollution. Because highway diesel and off-road diesel are essentially the same except for the dye and the taxes, they are both considered ULSD fuels.

What is the difference between auto diesel and truck diesel?

The equipment used to dispense the fuel and flow rates needed to pump the fuel into vehicles is really all that separates auto diesel from truck diesel. There is no difference when it comes to the chemical makeup of both fuels.

Auto diesel is pumped through fuel dispensers that serve light-duty road vehicles. Auto diesel fuel dispensers pump fuel at a rate of about 10 gallons per minute (gpm). Truck diesel is pumped through high-flow dispensers that serve heavy-duty road vehicles. Truck diesel dispensers are rated up to 50 gpm.

Heavy-Duty Filter Selection for Diesel Fuels

Luber-finer filters are compatible with petroleum diesel, biodiesel, biodiesel blends and renewable diesel. Because tougher emissions regulations have led to engines with high-pressure fuel systems, extremely clean fuel is needed to deliver improved fuel economy, proper fuel system function and reduced downtime.

A fuel filter’s micron rating is especially important for protecting diesel engines. According to a recent Diesel Fuel Quality Council (DFQC) report, diesel engines may be susceptible to damage from particulate as small as 4 microns.

From debris and particulates transported in fuel storage tanks to condensation and microbial growth in biofuels, Luber-finer’s heavy-duty spin-on cartridge fuel filters help maintain engine efficiency and performance.

You can use Luber-finer’s part search tool or the Luber-finer app to find the fuel filter that fits your specific heavy-duty application.